1. Field of the Invention.
The present invention relates, generally, to object proximity detection methods and apparatus. More particularly, the invention relates to object proximity detection methods using an optical sensor system that transmits and receives light radiation or optical signals. The optical signal may be steady-state, pulsed, digitally encoded, or a sequenced combination of the foregoing. The invention provides a means to control a variety of devices or processes based upon the presence or absence of an object within some predetermined distance from or orientation to a fixed sensor. An object is detected by transmitting digital data bursts of light radiation from a remote optical energy transmitter and verifying the error-free return of the digital data bursts into an optical energy receiver. The verification of the error-free return of the transmitted data bursts provides proof that, depending on the design of the sensor system, an object is either present and has reflected the optical energy into the receiver or is absent and has not blocked the optical energy from being received into the receiver.
The apparatus and methods of this invention have particular utility used in conjunction with commercial and institutional food service beverage and ice dispensing systems, medical/pharmaceutical dispensing systems, automated manufacturing and production systems, food processing systems, packaging systems, and a variety of other commercial, industrial, municipal and residential systems that utilize one or more mechanical, electronic, optical, or similar sensors in their operations.
2. Background Information.
The primary difficulty with using optical signals for object detection is distinguishing valid signals from ambient light energy noise. This invention employs digital data error detection principles to insure that the received signal accurately indicates the presence or absence of an object.
Noise rejection or avoidance in optical sensor systems has usually been attacked using one of two methods. The first method simply looks for "clean" time slots without noise and transmits signals during these clean time slots. The second method transmits a master-clocked continuous pulsed signal and a corresponding master-clocked synchronous signal, and verifies that the received signal exactly matches both the transmitted pulsed and synchronous signals. These described methods for rejecting or avoiding noise in optical sensor systems are generally disclosed in the following United States patents: Skell et al, U.S. Pat. No. 5,550,369; Skell et al., U.S. Pat. No. 5,491,333; Grozinger et al., U.S. Pat. No. 5,250,801; Schiller, U.S. Pat. No. 5,245,177; Kim, U.S. Pat. No. 4,973,834; Hatten et al, U.S. Pat. No. 4,282,430; Hosel, 5,002,102; Fukuyama et al., U.S. Pat. No. 4,306,147; Devale, U.S. Pat. No. 4,437,499; and Upton, U.S. Pat. No. 4,202,387.
This invention differs significantly from known art. No attempt is made to pre-filter the noise to a relatively low level with respect to the signal nor to identify "clean" time slots in which to transmit a signal. Moreover, this method does not depend on a master clock, a continuous pulsed signal, or a corresponding synchronous circuit. Rather, the present invention transmits a burst of digitally encoded data as required to control the equipment, system, or process that is the object of the design. Furthermore, both the data content and period between bursts are varied. This asynchronous transmission of digitally encoded data provides an effective method for distinguishing valid signals from ambient light energy noise.
An object of the invention is to provide a touchless, economical and reliable object proximity device using an optical sensor system. It is a further object of the invention to verify the presence of an object within a predetermined area using principles of digital data transmission, reception and error detection.